Hybrid concepts or purely electrical drive concepts which are employed in road transport as purely electric vehicles or as hybrid vehicles, have increasingly been developed for some time in order to reduce the emissions by motor vehicles which are driven by internal combustion engines. The operation of electrical machines which are required for this purpose in motor and generator mode requires a corresponding electrical energy store in the respective vehicle, wherein, specifically in the case of electrically driven vehicles, voltages of several hundred volts are often required and a battery which is used as the energy store has to provide powers of up to several hundred kilowatts in the process. Examples of batteries of this kind include, inter alia, combinations of individual rechargeable battery cells, called a traction battery, which, for reasons of a high degree of efficiency and a high storage capacity, have high voltage potentials which could constitute a hazardous source of danger to vehicle occupants and also to rescue service personnel in the event of an accident, also called a crash, for example on account of the danger of a fire, explosion or the like caused by said voltage potentials.
In order to firstly ensure the required operational reliability by maintaining the permissible voltage ranges of the rechargeable battery cells and secondly to provide safety in the event of an accident, so-called battery management systems are usually used. Said battery management systems are used, amongst other things, to prevent an uncontrolled short circuit of individual battery cells or of the entire battery, said short circuit potentially leading to the battery catching fire or exploding. Therefore, some of the known battery management systems are, amongst other things, also safety devices for reducing the danger to persons in the event of an accident with an entirely or partially electrically operated vehicle, which safety devices are designed in such a way that the connection of the main battery to the corresponding electronic loads can be interrupted in the event of an accident.
As an example of safety devices of this kind for avoiding high dangerous voltage potentials acting on individuals in the event of a crash, DE 10 2011 013 182 A1 describes a device on traction batteries for electric vehicles in which different disconnection devices are provided, said disconnection devices disconnecting the battery cells from one another and from the on-board electrical system of the vehicle in accordance with predetermined criteria. In this case, the disconnection devices are safety switches which can be manually operated and which comprise, amongst other things, a manual emergency switch and also a switching element for triggering the cell group disconnection process, which switching element can be activated by radio from the outside. In DE 10 2011 013 182 A1, the safety switches are designed as conventionally powered switching relays or electronic circuit breakers which require a current source in order to be operated.
A schematic illustration of an operating principle of an electronic circuit breaker of this kind can be found in FIG. 5 in which the circuit breaker 91 which can be electrically operated can disconnect an electrical connection between a battery 92 and a power receiver 93, for example an electric motor of an electric vehicle or of a hybrid vehicle. The electrical signals which are required for this purpose and by means of which the circuit breaker 91 can be controlled in order to interrupt the electrical connection may however no longer be trouble-free or no longer be provided at all as a result of an accident-related failure of the vehicle-internal conventional 12 V battery. Therefore, an interruption between the battery 92 and the power receiver 93 cannot always be reliably ensured. An electric vehicle or hybrid vehicle which is damaged by an accident and has a closed power connection between the battery and current collectors can however put first responders, rescue service personnel and the occupants themselves in great danger.